The invention relates to medical appliances, namely, to devices used in endovascular surgery and intervention cardiology for restoration of narrowed bifurcation sites of a lumen of blood vessels, and also for treatment of an artery in the presence of an unstable atherosclerotic plaque for prevention of its rupture and an acute artherothrombosis, which is a basic etiological factor of an acute myocardial infarction.
At present, modern diagnostic methods (computer tomography, intravascular ultrasonic research, intravascular ultrasound imaging), allow accurate visualization of an unstable plaque in a lumen of a coronal artery. The latter, irrespective of degree of an obturation of an arterial lumen, is the basic morphological substrate for development of an acute myocardial infarction. Eccentricity of an unstable plaque dictates its necessity for selective stenting, especially in case of hemodynamically insignificant stenosis.
Delivery of instruments or a pharmaceutical composition directly to a place of damage in a vessel by means of conduction catheters is generally applied in the practice of endovascular surgeries, including in intervention cardiology. Upon placing a conduction catheter in an orifice of a coronary artery or some other artery, a coronary conductor is moved into a lumen of a blood vessel to enable advancing various instruments (balloon catheters, stents). The stent delivery systems of delivery of stents in use today and the stents themselves have a standard configuration in the shape of a monorail (over-the-wire) balloon catheter with a cylindrical stent mounted on a dilated balloon. After stent positioning in the narrowed vascular segment, pressure is increased in a balloon catheter, thus forcing expansion of both the catheter, and the stent mounted on it. Thus, the normal diameter of an artery is restored.
At the same time, there is a problem of restoration of a normal lumen of arteries in a zone of their bifurcation. At present, such operations, as a rule, require use of two guiding wires (sometimes referred to as “conductors”) which are moved into the main blood vessel and a lateral branch, thus enabling simultaneous insertion of instruments into the blood vessels and performance of “kissing balloon dilatation”.
There is also a problem of accurate orientation of instruments or devices inserted by means of a guiding catheter. Such a problem, in particular, is very acute in the practice of arterial stenting. Stenting arteries in a zone of bifurcation, especially the coronary arteries, constitute one of the main problems in interventional cardiology. As such, the most difficult is the operation of stenting arteries close to a lateral branch (blood vessel). At present, the techniques of stenting are widely used in cases where the stent is implanted into the main artery, the wire is introduced in a lateral branch through a cell of the stent and definitive angiographic result of operation is generated after the balloon angioplasty of the bifurcation zone by two “kissing” balloons. The procedure of stenting bifurcation lesions of arteries is also carried out by two stents simultaneously (techniques: cullotte, crush, V-stenting, T-stenting), and is accompanied by the increased risk of damage of an arterial wall, high risk of restenosis and intra-operative technical difficulties.
The problem of complete optimization of the artery diameter in the bifurcation zone is a difficult problem if conventional stents are used. There are several types of special bifurcation stents (for example Frontier stent (Abbot Vascular Inc.)) where the technical result is achieved by application of two balloons and two conductors to which the stent is mounted and which are positioned both in the main artery and in a lateral branch.
Another group of bifurcation stents has a special mesh structure that has an aperture for the lateral branch (SLK-View™ stent, Stentys), that allows optimizing implantation of the second stent in the lateral branch. Also, the nitinol bifurcation stent AXXESS Plus, from Devax Inc., has certain clinical applications, and which has the shape of a truncated cone, thus, the basic advantage of this stent at stenting the main artery consists in lower probability of atheromatosis mass shift in the lateral branch. At the same time, all bifurcation stents used in the current clinical practice have a design which, to certain extent, provides for successful main artery stenting and reinforcing the orifice of a lateral branch, but coverage throughout a sufficient length of the lateral branch is not provided. The specialized stents have, as a rule, a complex design comprising two balloons, two conductors (guide wires) and a limited range of application.
Russian Federation patent No. 192810 describes a kit for transluminal introduction of a tubular stent, including a self-dilatable tubular stent representing a transplant and the device for introduction of the stent, is known. This kit does not solve the problem of the high-precision placement of the stent in an orifice of a lateral arterial branch.
Also known is an eccentric stent, dilatable (expandable) by means of a balloon catheter, for implantation in a lateral arterial branch (see the U.S. Patent Publication No. 2004/0186560). The design of this stent is adapted for implantation in the orifice segment of a lateral branch of a coronary artery. However, the system of radiopaque labels used in this design does not provide for accurate enough positioning of the truncated part of a stent in the orifice segment of an artery, which can essentially influence safety endovascular operations.
The most similar to the claimed invention is the technical solution described in U.S. Pat. No. 7,252,679. This technical solution describes a stent comprising: a thin-walled, multi-cellular, tubular structure with a length and having in the unexpanded and unbent position a longitudinal axis passing through the center of the stent; a proximal end and a distal end; a multiplicity of circumferential sets of strut members, longitudinally separated each from the other and each set of strut members forming a closed, cylindrical portion of the stent; the stent also having a proximal set of circumferentially arranged strut members located at the proximal end of the stent and the proximal set of strut members oriented in a first plane generally transverse to the longitudinal axis; a distal set of circumferentially arranged strut members located at the distal end of the stent and the distal set of strut members oriented in a second plane generally transverse to the longitudinal axis; and a plurality of central sets of circumferentially arranged strut members positioned between the proximal and distal sets of strut members each of said central sets of circumferentially arranged stent members oriented in the same direction, and the central sets of strut members meeting the proximal set of strut members along a third plane; the first plane of the most proximal set of strut members having an angulation between 15 and 75 degrees with respect to the longitudinal axis of the stent when the stent has been expanded within a vessel of the human body, and the first, second and third planes intersecting with one another. The stent is self-expandable and is mounted on a rapid exchange stent delivery catheter. For better navigation, the stent is provided with a radiopaque marker attached either to the most proximal or to most distal location on the most proximal set of strut members.
While the design of the deliverable part of the stent has certain merits, the navigation system represented by a sole radiopaque marker, offers limited help to a clinician as the position of the marker is described by one coordinate only.